Siemens Sinamics S120 Function Manual page 408

Function modules
7.11 Parallel connection of power units
● With multiple infeeds, power must be supplied to the systems from a common infeed
● A current reduction (derating) of 7.5 % must be taken into consideration, regardless of the
As Basic Line Modules have no current compensation control, the three-winding transformer,
power cabling and line reactors must meet the following requirements in order to provide a
balanced current:
● Three-winding transformer must be symmetrical, recommended vector groups Dy5d0 or
● Relative short-circuit voltage of three-winding transformer u
● Difference between relative short-circuit voltages of secondary windings Δu
● Difference between no-load voltages of secondary windings ΔU ≤ 0.5 %.
● Use of symmetrical power cabling between the transformer and the Basic Line Modules
● Using line reactors that match the Basic Line Modules
A double-tier transformer is generally the only means of meeting the requirements of a three-
winding transformer for this application. Line reactors must always be installed if other types
of three-winding transformer are used. Alternative solutions for obtaining a phase
displacement of 30 °, such as two separate transformers with different vector groups, cannot
be used due to the inadmissibly high tolerances involved.
6-pulse parallel connection of Basic Line Modules
With the 6-pulse parallel connection, up to four Basic line modules are supplied by a
common two-winding transformer on the line side and controlled by a common control unit.
12-pulse parallel connection of Basic Line Modules
For 12-pulse parallel connections, up to four Basic Line Modules are supplied by a three-
winding transformer on the line side. In this case, an even number of modules, i.e. two or
four, must be divided between the two secondary windings. The Basic Line Modules of both
subsystems are controlled by a common Control Unit - even though the input voltages are
30° out of phase.
There is also the redundant version with which two BLMs in each case are controlled by one
Control Unit.
406
point (i.e. the modules cannot be operated on different line supplies).
number of modules connected in parallel.
Dy11d0.
(cables of identical type with the same cross-section and length)
Line reactors can be omitted if a double-tier transformer is used and only one Basic Line
Module is connected to each secondary winding of the transformer.
≥ 4%.
k
Function Manual, (FH1), 01/2012, 6SL3097-4AB00-0BP2
≤ 5%.
k
Drive functions