Siemens Sinamics S120 Function Manual page 394

Function modules
7.9 Master/slave for Active Infeed
Topology
Figure 7-23
Master/slave operation can be implemented for a maximum of 4 Active Line Modules.
Electrical isolation of infeeds
To successfully implement the structure, a means of electrically isolating the infeeds from the
line supply is required in addition to the SINAMICS components. This is to prevent circulating
currents from developing if the pulse patterns of the Active Line Modules are not
synchronized.
392
Topology structure and communications network based on PROFIBUS for master/slave
operation with redundant infeeds (4 infeed trains)
Function Manual, (FH1), 01/2012, 6SL3097-4AB00-0BP2
Drive functions