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

12-pulse operation of SINAMICS G150 parallel converters

At 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
With SINAMICS G150 parallel converters, a correct 12-pulse operation can only be guaranteed when the following
supplementary conditions are met:
•
The DC links of both partial converters must be connected to each other.
•
It is possible to connect both motors with two electrically isolated winding systems and motors with one
common winding system.
As the line-side rectifiers have no electronic current sharing control, three-winding transformer, power cabling and
line reactors must meet the following requirements in order to provide a balanced current:
•
Three-winding transformer must be symmetrical, recommended vector groups Dy5d0 or Dy11d0.
•
Relative short-circuit voltage of three-winding transformer uk ≥ 4 %.
•
Difference between relative short-circuit voltages of secondary windings Δuk ≤ 5 %.
•
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 uk = 2 %. (Line reactors can be omitted if
a double-tier transformer is used and only one G150 parallel converter is connected to the
transformer).
The relatively high demands on the three-winding transformer can generally only be met by using a double-tier
transformer. In this case, the line reactors can be omitted. When using other types of three-winding transformers, line
reactors are, however, required. Alternative solutions for obtaining a phase displacement of 30 °, such as two
separate transformers with different vector groups, cannot be used due to the inadmissibly high tolerances involved.
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 motor-side limitations and restrictions are described on the following pages in the section "Operation at motors
with two electrically isolated winding systems and one common winding system".
Engineering Information
SINAMICS Engineering Manual - May 2008
© Siemens AG
SINAMICS G150
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