Siemens SINAMICS DCM Operating Instructions Manual page 456

Descriptions of functions
10.25 Connecting units in parallel and in series
Extended topology
The topology of a 6-pulse parallel connection, comprising a master converter, one substitute
master, two slave converters, as well as an independent converter is shown in the following
diagram.
The converters SINAMICS DCM 1, DCM 2, DCM 3 and DCM 4 are operated in the n+m
operating mode. The SINAMICS DCM 5 converter is, regarding its power unit, independent
of the others. It only exchanges BICOs with them via the parallel interface.
Figure 10-55 6-pulse parallel connection, extended topology
Operating modes of the 6-pulse parallel connection
There are 2 operating modes:
Standard mode:
A SINAMICS DCM is defined as the master. This unit carries out the closed-loop speed
control, the closed-loop armature-current control, the line synchronization tasks and
determines the firing points. The firing points and the thyristor pair to be fired are transferred
to the slave units; all the slaves then fire the thyristor pairs at these points.
n+m mode:
n+m converters are connected in parallel. When up to m converters fail (e.g. a fuse ruptures
in the power unit, a fault message occurs), operation is maintained without any interruption.
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Operating Instructions, 1.2012, C98130-A7066-A1-05-7619
SINAMICS DCM DC Converter