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

Descriptions of functions
10.25 Connecting units in parallel and in series
Remark
If the two partial converters operate in the following mode, the current ripple is significantly
higher than operation with the same firing angle. 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:
● low reactive power, but no reduction of the ripple:
Note
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.
10.25.6

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 the Preface).
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)
Remark:
The incoming AC voltage of the controlled converter should be 10% to 15% higher than that
at the uncontrolled converter, in order that the current can be reliably reduced down to 0.
468
→ operation with the same firing pulses (p51799 = 41)
→ operation with following control (p51799 = 42)
Operating Instructions, 1.2012, C98130-A7066-A1-05-7619
SINAMICS DCM DC Converter