Danfoss VLT AHF 005

frequency converter installations often show that the
performance of the lter is slightly better with a 2%
background distortion. However, the complexity of the grid
conditions and the mix of specic harmonics does not
provide a general rule about the performance on a
distorted grid. Illustration 3.3 and Illustration 3.4 show
worst-case performance deterioration characteristics with
the background distortion.
0 20 40 60 80 100
0
5
10
15
20
25
THvD 0%
THvD 2%
THvD 5%
Load [%]
THiD average [%]
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Illustration 3.3 AHF 005
0
10
20
30
40
50
60
0 20 40 60 80 100
Load [%]
THvD 0%
THvD 2%
THvD 5%
THiD [%]
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Illustration 3.4 AHF 010
Performance at 10% THDv has not been plotted. However,
the lters have been tested and can operate at 10% THDv,
but the lter performance can no longer be guaranteed.
The lter performance also deteriorates with the unbalance
of the supply. Typical performance is shown in
Illustration 3.5 and Illustration 3.6.
0% unbalance
1% unbalance
2% unbalance
3% unbalance
0 20 40 60 80 100
Load [%]
0
2
4
6
8
10
12
14
THiD [%]
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Illustration 3.5 AHF 005
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0
0 20 40 60 80 100
Load [%]
5
10
15
20
25
0% unbalance
1% unbalance
2% unbalance
3% unbalance
THiD average [%]
Illustration 3.6 AHF 010
3.1.1 Power Factor
In no-load conditions (the frequency converter is in stand-
by), the frequency converter current is negligible, and the
main current drawn from the grid is the current through
the capacitors in the harmonic lter. Therefore, the power
factor is close to 0, capacitive. The capacitive current is
approximately 25% of the lter nominal current (depends
on lter size, typical values of 20–25%). The power factor
increases with the load. Because of the higher value of the
main inductor L
0
in the VLT
®
Advanced Harmonic Filter
AHF 005, the power factor is slightly higher than in the
VLT
®
Advanced Harmonic Filter AHF 010.
Illustration 3.7 and Illustration 3.8 show typical values for
the true power factor on AHF 010 and AHF 005.
0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0,9
1
0 20 40 60 80 100
Load [%]
True Power Factor
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Illustration 3.7 AHF 005
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0,9
1
0 20 40 60 80 100
Load [%]
0
True Power Factor
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Illustration 3.8 AHF 010
Basic Operating Principle o... Design Guide
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