The Frequency Converter As A Low-Frequency Source Of Interference - Siemens SINAMICS G130 Engineering Manual

EMC Installation Guideline
Engineering Information
2.3.3

The frequency converter as a low-frequency source of interference

If SINAMICS converters are connected to a supply system with a purely sinusoidal voltage (generator or
transformer), the non-linear characteristics of the components in the line-side rectifier circuits cause non-sinusoidal
supply system currents to flow, which distort the voltage at the PCC (Point of Common Coupling). This low-frequency,
conducted effect on the line voltage is known as "Harmonic effects on the supply system" or "supply system
perturbation".
Measures for reducing low-frequency interference emissions
The harmonic effects on the supply system caused by SINAMICS converters largely depend on the type of rectifier circuit
used. The magnitude of the harmonic effects on the supply system can, therefore, be influenced by the selection of the type
of rectifier and by additional line side components such as line reactors or Line Harmonics Filters.
The highest level of harmonic effects on the supply system is generated by six-pulse rectifier circuits, which are used
with SINAMICS G130 and G150 converters as well as with S120 Basic Line Modules and Smart Line Modules.
Typical line current with 6-pulse rectifier circuits
A considerable reduction of harmonic effects on the supply system can be achieved by means of Line Harmonics
Filters for SINAMICS G130 and G150 converters or by means of 12-pulse rectifier configurations with SINAMICS
S120 Basic Line Modules and Smart Line Modules.
Typical line current of 6-pulse rectifiers with Line Harmonics Filters
The lowest level of harmonic effects on the supply system is generated with active rectifiers, which are used with
SINAMICS S150 converters and SINAMICS S120 Active Line Modules. In this case, current and voltage are virtually
sinusoidal.
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