12-Pulse Operation Of Sinamics G150 Parallel Converters - Siemens SINAMICS G130 Engineering Manual

SINAMICS G150
Engineering Information
5.9.2

12-pulse operation of SINAMICS G150 parallel converters

In 12-pulse operation, each of the two rectifiers is connected to one secondary winding of a three-winding
transformer, as illustrated in the following diagram.
12-pulse operation of SINAMICS G150 parallel converters
SINAMICS G150 parallel converters can operate satisfactorily in a 12-pulse circuit if the following supplementary
conditions are fulfilled:
·
The DC links are interconnected.
·
Motors with electrically isolated winding systems or with a common winding system can be connected.
As no line-side current compensation control is provided, the three-winding transformer, power cabling and line
reactors (if installed) must meet the following requirements in order to provide a balanced current. Furthermore, no
additional loads may be connected to only one of the two low-voltage windings as this would prevent symmetrical
loading of both low-voltage windings. Furthermore, the connection of more than one 12-pulse converter to a three-
winding transformer should be avoided.
·
Three-winding transformer must be symmetrical, recommended vector groups Dy5d0 or Dy11d0.
·
Relative short-circuit voltage of three-winding transformer v
·
Difference between relative short-circuit voltages of secondary windings Δv
·
Difference between no-load voltages of secondary windings ΔV ≤ 0.5 %.
·
Use of symmetrical power cabling between the transformer and the two rectifiers (cables of
identical type with the same cross-section and length)
·
Use of line reactors with a relative short-circuit voltage of v
A double-tier transformer is generally the best means of meeting the relatively high requirements of the three-winding
transformer. When other types of three-winding transformer are used, it is advisable to install line reactors.
Alternative solutions for obtaining a phase displacement of 30 °, such as two separate transformers with different
vector groups, should be used only if the transformers are practically identical (excepting their different vector
groups), i. e. if both transformers are supplied by the same manufacturer.
Since the three-winding transformer is equipped with a star and a delta winding, and the delta winding does not have
a star point that is suitable for grounding, 12-pulse-operated SINAMICS G150 parallel connections are connected to
two non-grounded secondary windings and, in turn, to an IT supply system. For this reason, G150 parallel
connections in 12-pulse operation must be equipped with Option L87 / insulation monitor.
The supplementary conditions to be fulfilled on the motor side are described on the following page in section
"Operation of motors with electrically isolated and with common winding systems".
SINAMICS Engineering Manual – November 2015
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Ó Siemens AG
≥ 4 %.
k
≤ 5 %.
k
= 2 %, if applicable.
k