Siemens SINAMICS G130 Engineering Manual page 194

Fundamental Principles and System Description
Engineering Information
The following S120 Modules can be connected in parallel:
·
Basic Line Modules, 6-pulse and 12-pulse (with the relevant line reactors in each case)
·
Smart Line Modules, 6-pulse and 12-pulse (with the relevant line reactors in each case)
·
Active Line Modules (with the relevant Active Interface Modules in each case)
·
Motor Modules in vector control mode (drive objects of vector type)
It is important to note that the parallel-connected Infeed Modules or Motor Modules, which are absolutely identical to
the corresponding modules for single drives in terms of hardware, must be of exactly the same type and for the same
rated voltage and rated output. The firmware versions and version releases of the CIM modules must also be
identical. It is therefore not permissible to mix different variants of Infeed Module within the same parallel connection
(e.g. a mixture of Basic Line Modules with Smart Line Modules or Basic Line Modules with Active Line Modules).
The diagram below shows the basic design of a SINAMICS S120 converter parallel connection.
Principle of the SINAMICS S120 converter parallel connection
As a result of unavoidable tolerances in the electrical components (e.g. diodes, thyristors and IGBTs) and imbalances
in the mechanical design of the parallel connection, symmetrical current distribution cannot be assured automatically.
The mechanical dimensions of the converters are particularly large with multiple parallel connections, resulting
inevitably in imbalances in the busbars and cabling which have a negative impact on current distribution.
There is a range of different measures which can be taken to ensure symmetrical current distribution between the
parallel-connected power units:
·
Use of selected components with low forward voltage tolerances (this option is not, however, used on
SINAMICS equipment due to a variety of disadvantages associated with it, e.g. high costs and problems
with spare parts stocking)
·
Use of current-balancing system components such as line reactors or motor reactors
·
Use of the most symmetrical mechanical design that is possible
SINAMICS Engineering Manual – November 2015
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Ó Siemens AG