Harmonic Currents Of 12-Pulse Rectifier Circuits - Siemens SINAMICS G130 Engineering Manual

Fundamental Principles and System Description
Engineering Information
Typical line current of 6-pulse rectifiers with Line Harmonics Filters (LHF)

Harmonic currents of 12-pulse rectifier circuits

A 12-pulse rectifier circuit is created when two identical 6-pulse rectifiers are supplied from two different supply
systems, whose voltages are out of phase by 30°. This is achieved with the use of a three-winding transformer,
whose one low-voltage winding is star-connected and the other delta-connected. The harmonic effects can be
significantly reduced with 12-pulse circuits as compared to 6-pulse circuits. 12-pulse rectifier circuits can be
implemented for SINAMICS G150 in the higher power range, which consists of the parallel connection of two
individual G150 devices and therefore two 6-pulse rectifiers. 12-pulse rectifier circuits can also be implemented by
using two S120 Basic Line Modules or S120 Smart Line Modules.
12-pulse rectifier with separate three-winding transformer
Due to the phase shifting of 30° between the two secondary voltages, the harmonic currents with harmonic numbers
h = 5, 7, 17, 19, 29, 31, 41, 43, ... , which are still present in the input currents of the 6-pulse rectifiers, compensate
one another so that theoretically only odd harmonic currents and voltages that cannot be divided by 3 with the
following numbers h occur at the PCC on the primary side of the three-winding transformer:
h = n 12 ± 1
*
i.e.
h = 11, 13, 23, 25, 35, 37, 47, 49, ...
SINAMICS Engineering Manual – May 2008
44/396
© Siemens AG
where n = 1, 2, 3, ...