Siemens SINAMICS DCM Manual page 580

Remark
The current ripple is significantly higher during during operation with sequence control than
operation with the same firing pulses. 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 pulses (p51799 = 41)
● Low reactive power, but no reduction of the ripple:
→ Operation with sequence control (p51799 = 42)
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.
SINAMICS DCM DC Converter
Operating Instructions, 02.2015, A5E34763375/RS-AA/001
10.27 Connecting units in parallel and in series
ac.maher.co.ir
Descriptions of functions
581