Harmonic Currents Of 6-Pulse Rectifier Circuits; Sinamics G130, G150, S120 Basic Infeed And S120 Smart Infeed In Motor Operation - Siemens SINAMICS G130 Engineering Manual

Fundamental Principles and System Description
Engineering Information
·
The harmonic currents (harmonic numbers which occur and their amplitudes) are mainly determined by the
rectifier circuit type of the converter and are therefore device-specific. The transformer and the supply system for
the transformer have a relatively small effect on the harmonic currents. This means that when the rectifier circuit
type is known, the approximate magnitude of the harmonic currents is also defined and detailed information
about the transformer and the supply system are not required.
·
The harmonic voltages (harmonic numbers which occur and amplitudes) are determined by the interaction
between the rectifier circuit of the converter and the transformer including the supply system. As they require
knowledge of the supply system and transformer data, these are system-specific and it is not therefore easy to
make general statements about their possible impact.
The following sections provide detailed information about the various types of rectifier circuits used with SINAMICS
and their harmonics currents.
It is assumed that there are no non-reactor-protected compensation systems in the line supply to which the variable-
speed drives are connected. When a supply system includes capacitors without reactor protection for reactive power
compensation, it is highly probable that resonances excited by the harmonics of the converters will occur at relatively
low frequencies. Therefore, it is strongly recommended that capacitors without reactor protection are not used in
supply systems loaded by converters and that all capacitors used in such constellations must have reactor protection.
1.4.2

Harmonic currents of 6-pulse rectifier circuits

1.4.2.1

SINAMICS G130, G150, S120 Basic Infeed and S120 Smart Infeed in motor operation

6-pulse rectifier circuits are line-commutated three-phase bridge circuits, which usually are equipped with thyristors or
diodes. They are used with SINAMICS G130 (thyristors), G150 (thyristors) and S120 Basic Line Modules (thyristors
for low power outputs and diodes for larger outputs). A line reactor with a relative short-circuit voltage of 2 % is
usually connected in series with these rectifiers.
With the rectifier / regenerative feedback units SINAMICS S120 Smart Line Modules which are equipped with IGBT
modules, the rectifier bridge for motor operation consists of the diodes integrated into the IGBT modules, so that a 6-
pulse diode bridge circuit is present during rectifier operation (motor operation). A line reactor with a relative short-
circuit voltage of 4 % is normally connected in series with the Smart Line Modules.
6-pulse three-phase bridge circuit with thyristors
With 6-pulse rectifier circuits, only odd harmonic currents and odd harmonic voltages that cannot be divided by 3
occur, with the following harmonic numbers h:
h = n 6 ± 1
*
i.e.
h = 5, 7, 11, 13, 17, 19, 23, 25, 29, 31, 35, 37, 41, 43, 47, 49, ...
The order of magnitude of the individual harmonic currents with the above harmonic numbers is mainly determined
by the 6-pulse rectifier circuit. However, the power supply inductance, which mainly consists of the inductance of the
supply transformer, and the inductance of the line reactor also have a certain effect. The larger these inductances
are, the better the line current is smoothed and the lower the harmonic currents are, especially the harmonic currents
with numbers 5 and 7.
SINAMICS Engineering Manual – November 2015
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Ó Siemens AG
where n = 1, 2, 3, ...