Siemens SIROTEC Engineering Manual

Fundamental Principles and System Description
Engineering Information
SINAMICS Engineering Manual – November 2015
Ó Siemens AG
78/528
Line Harmonics Filters 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 where n = 1, 2, 3, ...
i.e.
h = 5, 7, 11, 13, 17, 19, 23, 25, 29, 31, 35, 37, 41, 43, 47, 49, ...
Even when Line Harmonics Filters (LHF or LHF compact) are used, the supply system inductance has a certain
effect on the magnitude of the harmonic currents, but this is significantly lower than with 6-pulse rectifiers without Line
Harmonics Filters.
The typical harmonic currents of 6-pulse rectifiers with Line Harmonics Filters (LHF or LHF compact) 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
k
Line
at the PCC is significantly higher than the apparent power of the connected
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 7 11 13 17 19 23 25 THD(I)
I
h
100 % 4.5 % 4.7 % 2.8 % 1.6 % 1.2 % 0.9 % 0.6 % 0.5 % 7.5 %
Supply system with average relative short-circuit power (RSC = 50)
h 1 5 7 11 13 17 19 23 25 THD(I)
I
h
100 % 4.2 % 4.4 % 2.6 % 1.4 % 1.2 % 0.8 % 0.6 % 0.5 % 7.0 %
Supply system with low relative short-circuit power (RSC < 15): "Weak supply system“
h 1 5 7 11 13 17 19 23 25 THD(I)
I
h
100 % 2.9 % 3.1 % 1.8 % 1.3 % 1.1 % 0.7 % 0.6 % 0.5 % 5.0 %
Typical harmonic currents of 6-pulse rectifiers with Line Harmonics Filters LHF
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
0
10
20
30
40
50
60
70
80
90
100
1 3 5 7 9 11 13 15 17 19 21 23 25

Siemens SIROTEC Specifications

General

Brand	Siemens
Model	SIROTEC
Category	DC Drives
Language	English