Depending on the application and the type of static excitation equipment used, line-side
components such as a transformer or line reactors may be required for excitation purposes if
their monitoring and control functions are not provided by the converter.
Note
The premagnetization of the converter transformer is not part of the converter.
4.1.2 Selection and configuration of multi-winding transformers
Multi-winding transformers supply converters which are connected separately, in parallel, or
in series. In general, transformers are configured for a line voltage range of ±5% in accordance
with IEC 60076-1 (they may be configured differently on request).
Coupling factor
Each converter causes current harmonics as a result of non-sinusoidal input currents and
commutation processes. These current harmonics distort the voltage, which results in a
deformation of the supply voltage for subsequent windings. This can cause a malfunction in
the case of controlled line-side converters. In critical cases, ensure that the degree of coupling
is less than 10 to 15% and that the degree of decoupling is between 85 and 90%.
Design of the transformer winding
① Core
Figure 4-1 Two-tier design
Transformers for start-up operation
For short-time operation, the converter as well as the associated step-down and step-up
transformer (if being used) are utilized to a higher degree. In the case of starting converters
in the LCI design version, usually only the DC link reactor is affected. If just one or two motors
have to start up consecutively, the transformers can be significantly overloaded. In this case
the only limits are thermal load capacity of the winding and the iron core. When specifying/
ordering the transformer, mention heavy-duty starting (>> 2 min).
Preparations for use
4.1 Notes for system integrators
SINAMICS GL150 6SL38503UM114PA0Z
50 Operating Instructions 04/2017
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