Lenze i410 - Square-Law V;F Characteristic

9.2.3.2 Square-law V/f characterisc
The square-law V/f characterisc is typically used in heang, venlaon and climate
applicaons to control the speed of fans and centrifugal pumps.
Details
Each applicaon that is provided with the features according to the anity laws may possibly
benet from a square-law V/f characterisc.
The
anity laws describe the relaon between the speed and other variables:
•
The volume ow increases proporonately to the speed.
•
The required pressure behaves proporonately to the square of the speed.
•
The power input is proporonately to the cube of the speed. This means that already a
minimal reducon of the speed may lead to substanal savings in energy consumpon.
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50 100
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100
0
[%]
[%]
0
50 100
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100
0
[%]
[%]
0
50 100
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100
SpeedSpeedSpeed
Power inputPressureVolume flow
By approximaon, the square-law V/f characterisc corresponds to the curve for power input
sho
wn above. At low frequencies, the voltage is reduced since due to the type of load a lower
voltage is sucient to generate the required power. All in all, this results in an energy-ecient
system.
Select V/f characterisc control with square-law characterisc:
1.
Mot
or control mode 0x2C00 (P300.00) = "V/f characterisc control (VFC open loop) [6]"
2.
V
/f characterisc shape 0x2B00 (P302.00)= "Quadrac [1]"
Seng of the V/f characterisc:
•
Liming factors for the V/f characterisc are the rated mains voltage 0x2540:001
(P208.01), the minimum fr
equency 0x2915 (P210.00) and the maximum frequency
0x2916 (P211.00).
•
The base voltage 0x2B01:001 (P303.01) is usually set to the rated motor voltage (motor
nameplate data). The base voltage is preset to the rated mains voltage. This in turn is
preset according to the product key of the inverter. 4Mains voltage ^ 31
•
The base frequency 0x2B01:002 (P303.02) is usually set to the rated motor frequency
(motor nameplate data).
0
[V]
[Hz]
0
0x2540 001:
0x2B01 001:
0x2B01 002:
0x29160x2915
The actual output frequency can exceed the set maximum frequency if the gain
f
or the slip compensaon in 0x2B09:001 (P315.01) is set to a value higher than
0.
Conguring the motor control
V
/f characterisc control for asynchronous motor (VFC open loop)
Dene V/f characterisc shape
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