Siemens SINAMICS G130 Engineering Manual page 40

Fundamental Principles and System Description
Engineering Information
6-pulse rectifier with line reactor on a three-phase supply
Typical harmonic currents of a 6-pulse rectifier with an line reactor are specified in the following (relative short-circuit
voltage of the line reactor = 2 %).
These data are based on three different supply system constellations with differences in supply system inductance or
relative short-circuit power RSC (RSC = Ratio of the short-circuit power S
frequency apparent power S
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. This is
the case, for example, when a converter with an apparent power of a few 100 kW is connected to a supply
system which is supplied via a transformer with an apparent power of several MVA.
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 % 45.8 %
h
Supply system with average relative short-circuit power (RSC = 50)
h 1 5
I 100 % 37.1 %
h
Supply system with low relative short-circuit power (RSC < 15) "Weak supply system"
h 1 5
I 100 % 22.4 %
h
Typical harmonic currents of 6-pulse rectifier with line reactors u
100
90
80
70
60
50
40
30
20
10
0
1 3 5 7
Spectral representation of the harmonic currents of a 6-pulse rectifier with line reactor u
- Bars on left:
- Bars in center:
- Bars on right:
SINAMICS Engineering Manual – May 2008
40/396
© Siemens AG
of the connected converters).
Converter
at the PCC is significantly higher than the apparent power of the connected
Line
k
7 11
21.7 % 7.6 %
7 11
12.4 % 6.9 %
7 11
7.0 % 3.1 %
9 11 13 15 17 19 21 23 25
RSC >> 50
RSC = 50
RSC < 15
k Line
13 17 19
4.6 % 3.4 % 1.9 %
13 17 19
3.2 % 2.8 % 1.9 %
13 17 19
2.5 % 1.3 % 1.0 %
= 2 %
k
at the PCC to the fundamental
23 25 THD(I)
1.9 % 1.1 % 51.7 %
23 25 THD(I)
1.4 % 1.3 % 40.0 %
23 25 THD(I)
0.8 % 0.7 % 23.8 %
= 2 % (specified in %)
k