Siemens SINAMICS S120 Function Manual page 330

Function modules
7.11 Parallel connection of power units
Active Line Modules (ALM)
Features
Active Line Modules can supply the motor with power and recover energy produced in
generator mode back to the power network.
The parallel connection of up to four Active Line Modules is supplied by a shared two-
winding transformer and controlled synchronously by a shared Control Unit. The modules
must not be connected to the supply via a three-winding transformer with phase-displaced
secondary voltages.
Active Line Modules produce a stabilized DC voltage that remains constant regardless of
fluctuations in the line voltage (the line voltage must range within the permissible tolerances).
The DC link voltage is greater than the rms value of the line rated voltage by a factor of 1.5.
Active Line Modules draw a virtually sinusoidal current from the supply system and cause
virtually no line harmonic distortions.
Active Line Modules are available for the following voltages and power ratings:
Line voltage / unit rating
380 ... 480 V 3 AC / 132 ... 900 kW
500 ... 690 V 3 AC / 560 ... 1400 kW
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 shared Control Unit must be used to implement the parallel connection.
● Special Line Connection Modules are available for connecting the modules in parallel.
● With multiple infeeds, power must be supplied to the systems from a common infeed
● A derating factor of 5% must be taken into consideration, regardless of the number of
The following measures help to ensure balanced currents in parallel connections of Active
Line Modules:
● Reactors in the Clean Power Filters of the Active Interface Modules.
● Use of symmetrical power cabling between the transformer and the parallel-connected
● The current reduction from the rated value for individual Active Interface Modules / Active
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point (i.e. the modules cannot be operated on different supplies).
modules connected in parallel.
Active Interface Modules / Active Line Modules (cables of identical type with the same
cross-section and length).
Line Modules in a parallel connection is 5 %.
Function Manual, (FH1), 10/2008, 6SL3097-2AB00-0BP5
Drive functions