Siemens SINAMICS G130 Engineering Manual page 43

6-pulse rectifier with line reactor and Line Harmonics Filter LHF on a three-phase supply
Line Harmonics Filter LHF influence only the magnitude of the harmonic currents, but not their spectrum. As a
consequence, therefore, the 6-pulse rectifier causes odd harmonic currents and voltages that cannot be divided by 3
despite the use of a Line Harmonics Filter. The harmonic numbers h are as follows:
h = n 6 ± 1
*
i.e.
h = 5, 7, 11, 13, 17, 19, 23, 25, 29, 31, 35, 37, 41, 43, 47, 49, ...
Even when Line Harmonics Filters are used, the supply system inductance has a certain effect on the magnitude of
the harmonic currents, but this is, however, far less than with 6-pulse rectifiers without Line Harmonics Filters.
The typical harmonic currents of 6-pulse rectifiers with Line Harmonics Filters LHF are specified below.
These data again are based on three different supply system constellations with differences in supply system
inductance or relative short-circuit power RSC.
a) Supply system with low supply system inductance or high relative short-circuit power (RSC >> 50)
The short-circuit power S
converters, i.e. only a relatively small percentage of the transformer load is attributable to the converter.
b) Supply system with average supply system inductance or average relative short-circuit power (RSC = 50)
This applies, for example, when approximately 30 % to 50 % of the transformer load is attributable to the
converter.
c) Supply system with high supply system inductance or low relative short-circuit power (RSC < 15)
This is the case when 100 % converter load is connected to a transformer with a high short-circuit voltage, i.e
only one converter whose apparent power approximately corresponds to the apparent power of the transformer.
Supply system with high relative short-circuit power (RSC >> 50): "Strong supply system"
h 1 5
I 100 % 4.5 %
h
Supply system with average relative short-circuit power (RSC = 50)
h 1 5
I 100 % 4.2 %
h
Supply system with low relative short-circuit power (RSC < 15): "Weak supply system"
h 1 5
I 100 % 2.9 %
h
Typical harmonic currents of 6-pulse rectifiers with Line Harmonics Filters LHF
100
90
80
70
60
50
40
30
20
10
0
1 3 5 7
Spectral representation of the harmonic currents of 6-pulse rectifiers with Line Harmonics Filters (specified in %)
- Bars on left: RSC >> 50
- Bars in center: RSC = 50
- Bars on right: RSC < 15
Fundamental Principles and System Description
where n = 1, 2, 3, ...
at the PCC is significantly higher than the apparent power of the connected
Line
k
7 11
4.7 % 2.8 %
7 11
4.4 % 2.6 %
7 11
3.1 % 1.8 %
9 11 13 15 17 19 21 23 25
13 17 19
1.6 % 1.2 % 0.9 %
13 17 19
1.4 % 1.2 % 0.8 %
13 17 19
1.3 % 1.1 % 0.7 %
SINAMICS Engineering Manual - May 2008
Engineering Information
23 25
0.6 % 0.5 %
23 25
0.6 % 0.5 %
23 25
0.6 % 0.5 %
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© Siemens AG
THD(I)
7.5 %
THD(I)
7.0 %
THD(I)
5.0 %