Line Harmonics Filters (Lhf And Lhf Compact); Operating Principle Of Line Harmonics Filters (Lhf And Lhf Compact) - Siemens SINAMICS G130 Engineering Manual

Permissible cable length between line reactor and converter
Line reactors should be positioned directly at the converter input whenever possible. In individual cases, however, the
low frequencies involved make it possible to situate the line reactor at a greater distance from the converter, provided
that the cable length does not exceed 100 m. Exception: Converters with optional line filters for category C2 in
accordance with EN 61800-3 require the line reactor and line filter to be positioned directly at the converter input (see
also section "Line filters").
1.5.2

Line Harmonics Filters (LHF and LHF compact)

1.5.2.1

Operating principle of Line Harmonics Filters (LHF and LHF compact)

Line Harmonics Filters (LHF und LHF compact) are passive LC filters that mainly filter out the 5th and the 7th
harmonics in the line current of 6-pulse rectifiers and in this way significantly reduce the harmonic effects at the PCC.
Compliance with the limit values defined in standard EN 61000-2-4 / Class 2 and the very low limit values defined in
standard IEEE 519 (Recommended Practices and Requirements for Harmonic Control in Electrical Power Systems)
is therefore assured.
Two versions of Line Harmonics Filters are available, i.e. LHF and LHF compact. They can be used for
SINAMICS G130 units (LHF only) and G150 units (LHF and LHF compact). They are installed between the supply
system and the converter. Line Harmonics Filters (LHF) form an oscillating circuit at the converter side together with
the line reactor of the converter which must be installed between the LHF and the converter input, and they form an
oscillating circuit at the line side together with the supply inductance. There is no need to install a line reactor at the
converter input for Line Harmonics Filters compact (LHF compact).
The oscillating circuit on the converter side consists of the Line Harmonics Filter and the line reactor at the
converter input with a relative short-circuit voltage v
should, as far as possible, absorbe the current harmonics produced by the converter and should, therefore, prevent
these harmonics from successfully entering the supply. Its resonant frequency is therefore designed for the largest
th
harmonic, i.e. the 5 , so that the 5
th
7 current harmonic of the converter is also absorbed significantly and even the 11
absorbed. In the following diagram, the solid, black line shows the filter characteristics on the converter side. It is a
measure of how much each individual harmonic produced by the converter will be reduced by the LHF and also of
how much the power supply will consequently get rid of the harmonics.
Schematic diagram of the Line Harmonic Filter and the converter-side / line-side filter characteristics (qualitative analysis)
The spectrum diagrams illustrate the typical harmonic currents, both at the converter side where they are produced,
and at the line side after the Line Harmonics Filter (LHF or LHF compact) has reduced them according to its
converter-side filter characteristics. Further information on the harmonic currents of Line Harmonics Filter can be
found in the section "Harmonic effects on the supply system".
100
90
80
70
60
50
40
30
20
10
0
1 3 5 7 9 11 13 15 17 19 21 23 25
a) Typical spectrum of the harmonic currents on the
converter side (specified in %)
Fundamental Principles and System Description
= 2 % (not applicable to LHF compact). This oscillating circuit
k
th
current harmonic of the converter is almost completely absorbed by the filter. The
b) Typical spectrum of the harmonic currents on the line
SINAMICS Engineering Manual – November 2015
Engineering Information
100
90
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40
30
20
10
0
1 3 5 7 9 11 13 15 17 19 21 23 25
side after filtering (specified in %)
Ó Siemens AG
th th
and the 13 are partly
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