Siemens SINAMICS G130 Engineering Manual page 120

Fundamental Principles and System Description
Engineering Information
Comments on c)
The variant with winding systems that are completely electrically isolated and out of phase is not suitable for parallel
connections of SINAMICS converters, as the pulse patterns of the parallel-connected Motor Modules are
synchronized by the Control Unit and are therefore absolutely identical.
These types of winding were previously used in conjunction with parallel connections of current-source DC link
converters SIMOVERT A in 12-pulse operation. As a result, windings of this type may exist in installations where
older models of current-source DC link converter are replaced by SINAMICS, but the motors are to be retained.
Comments on d)
This variant with separate winding systems at the input side and internally coupled neutral is essentially a hybrid of
variants a) and b). The problem with this variant is that circulating currents can develop between the systems due to
the electrically coupled neutrals. These currents increase the losses in the motor and can therefore lead to a
significant temperature rise in the motor. This risk of motor overheating is the reason why this variant cannot be used
in parallel connections of SINAMICS converters.
SINAMICS Engineering Manual – May 2008
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