Siemens SINAMICS S120 System Manual page 144

Device overview
8.4 Air-cooled Active Line Modules for the grid infeed, chassis format
Parallel connection of Active Line Modules to increase power rating
To increase the power and for redundancy, it is possible to connect up to four Active Line
Modules each with the same output rating and type in parallel.
The following rules must be observed when connecting Active Line Modules in parallel:
● Up to 4 identical Active Line Modules can be connected in parallel.
● A common Control Unit is required whenever the modules are connected in parallel.
● With multiple infeeds, power must be supplied to the systems from a common infeed
point (i.e. different supply systems are not permitted).
● A derating factor of 5% must be taken into consideration, regardless of the number of
modules connected in parallel.
Note
It is only possible to connect identical power units in parallel if both power units have the
same hardware version.
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System Manual, 04/2015, A5E03347436A
Grid infeed