Siemens SINAMICS S120 Function Manual page 570

Function modules
8.10 Parallel connection of power units
Owing to the electrical isolation of the winding systems, this arrangement offers the following
advantages:
● Decoupling measures are not required at the infeed output in order to limit any potential
circulating currents between the parallel-connected Motor Modules (no minimum cable
lengths and no motor reactors).
● Both types of modulation system, i.e. space vector modulation and pulse-edge
modulation can be used, i.e. when the parallel connection is supplied by Basic Line
Modules or Smart Line Modules, the maximum obtainable output voltage is almost equal
to the three-phase AC line voltage connected to the infeeds (97%). When the parallel
connection is supplied by Active Line Modules, a higher output voltage than the input
voltage at the three-phase end can be obtained due to the increased DC-link voltage.
For a parallel connection, the current reduction referred to the rated value for the individual
Motor Modules is 5%.
Parallel connection of two Active Line Modules and two Motor Modules on a motor with a single
winding system
In many cases, it is not possible to use motors with separate winding systems, for example,
in the following cases:
● The required number of separate winding systems cannot be realized due to the pole
number
● The motor is a third-party motor
● A motor with a common winding system is already present.
In such cases, the outputs of the Motor Modules connected in parallel are interconnected via
the motor cables in the motor terminal box.
Active Interface Modules isolate switching-frequency harmonics from the supply connection
and thus effect basic interference suppression of the supply system. These modules are
essential to the operation of Active Line Modules. The VSM10 Voltage Sensing Module also
helps Active Line Modules to operate properly when mains power conditions are less than
ideal (e.g. severe voltage fluctuations, brief interruptions in the line voltage). VSMs are
integrated as standard in the Active Interface Modules for Active Line Modules in chassis
format.
570
Function Manual, 11/2017, 6SL3097-4AB00-0BP5
Drive functions