4-2-10-1_VFD_MINIMUM_REGULA
TION_138
Minimum control
Related information
8.2.10 Automatic energy optimisation(operation)
This function can only be used if a power meter (MP 204
or CUE/VFD) and flowmeter are installed in the system.
Flow calculation can be used instead of a flowmeter.
"Automatic energy optimisation" is used to optimise the "Economy
frequency" during operation. The specific energy Q [kWh/m
3
] is
measured for each pump cycle (Start → Stop). When the pump is
started for the first time, the default "Economy frequency", f
ECO
, is
used. The next time the pump starts, the f
ECO
+ 1 Hz is used as
setpoint.
•
If Q f
ECO
+ 1 Hz is lower, the frequency is increased by 1 Hz.
•
If Q f
ECO
+ 1 Hz is higher, the frequency is reduced by 1 Hz.
This process continues until the lowest specific-energy consumption
is found. When the f
ECO
is optimised, this frequency is used over
the next 24 hours. After 24 hours, a new "Automatic energy
optimisation" routine is initiated to ensure that the pump runs with
an optimised frequency.
If "Start flushing" is enabled, this function runs before the
"Automatic energy optimisation" function.
To ensure a reliable measurement, a 5-second delay has to pass
before the measurement is started. The delay timer is started when
the "Economy level" is reached. See the figure below.
Level
Start
ECO
Stop
5.sec
Valid data
TM046709
Measurement delay
If the "Economy level" is higher than the "Start level", the
measurement is started 5 seconds after the "Start level" is reached.
Level
Start
ECO
Stop
5.sec
Valid data
TM046709
Measurement delay (Start level > Economy level)
If the flow into the pit is larger than the flow out of the pit,
the pump and the measurement are stopped.
If the pump has been in operation for more than 10 minutes, it will
be stopped. The specific energy measured during this period will be
used. If another pump is started during the measurement, it will be
stopped, and the measured specific energy will not be used.
8.2.11 Specific-energy test (installation)
This function can only be used if a power meter (MP 204
or CUE/VFD) and flowmeter are installed in the system.
Flow calculation can be used instead of a flowmeter.
The specific-energy test can be used during installation
(commissioning) to check the pit performance and to find f
min.
. This
function can be activated when one of these control modes is
selected:
•
Linear control
•
Minimum control.
The function must be enabled. Some parameters must be entered
before the test is started:
•
Measurement settling time
•
Max. offset below start level.
Measurement settling time
"Measurement settling time" (x) is a delay set in seconds and is the
time that has to pass before the measurement is started after the
"Economy level" is reached.
Max. offset below start level
As the specific energy may change when pumping from a filled pit,
compared to a nearly empty pit, the "Max. offset below start level"
can be set so that no energy test is made, both in a filled and an
empty pit. The "Max. offset below start level" is the distance below
the start level to where the energy test must be active. If the water
level falls below this level during the energy test, the rest of the
test is not continued before the start level is reached again. The
"Max. offset below start level" ensures a realistic energy test.
The specific-energy test can be used with benefit during installation
(commissioning) to give an indication of the "Economy frequency"
and "Min. frequency" for the actual application. When the function is
active, only one pump is running to give a reliable result. When the
test is started, 50 Hz is used as reference, and the pump ramps
down with 2 Hz per 2 × "Measurement settling time". See the figure
below.
Start
Stop
P1
f [Hz]
50
48
46
44
X
2X
TM046710
Specific-energy test
Based on the measurements, a diagram is created and can be
viewed by pressing [OK] in the line "Specific-energy diagram". The
actual test frequency and actual specific energy are shown in the
display. See section about specific-energy diagram.
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English (GB)
