12-Pulse Series Connection: Controlled Converter + Uncontrolled Converter - Siemens SINAMICS Series Operating Instructions Manual

Descriptions of functions
10.28 Connecting units in parallel and in series
Remark
The current ripple is significantly higher when the two partial converters operate with
sequence control than when they operate with the same firing times. In this case, the current
ripple approximately corresponds to that for 6-pulse operation. Especially in older motors,
under certain circumstances this ripple can cause problems (for example, during
commutation).
Therefore, a conscious decision must be made:
● Low ripple, but no reduction of the reactive power:
→ Operation with the same firing times (p51799 = 41)
● Low reactive power, but no reduction of the ripple:
→ Operation with sequence control (p51799 = 42)
Note
Connecting the slave converter to the 12-pulse transformer
The power unit of the slave converter must be connected to the 12-pulse transformer so that
its phases lag the phases of the line supply at the master by 30°. The phase sequence must
be the same.
10.28.6

12-pulse series connection: controlled converter + uncontrolled converter

Note
12-pulse applications
The circuit diagrams in this chapter are block diagrams.
You can find detailed information on interconnecting, dimensioning and parameterizing in the
application document "12-pulse applications".
Support is also available through our Technical Support organization (for contact address,
see "Preface (Page 3)").
Topology
The following diagram shows the topology of a 12-pulse series connection of a SINAMICS
DCM 2-quadrant unit and a diode rectifier (thyristor bridge B6 + diode rectifier).
Note
The AC input voltage of the controlled converter should be between 10% and 15% higher
than that of the uncontrolled converter, so that the current can be reliably reduced down to 0.
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SINAMICS DCM DC Converter
Operating Instructions, 12/2018, A5E34763375A