Siemens SINAMICS G130 Engineering Manual page 113

With variant 1, both redundant Infeeds with the same power rating are supplied from one supply system via a two-
winding transformer. As both Infeeds are supplied with exactly the same voltage on the line side, in normal operation
the current distribution is largely symmetrical, even with unregulated Infeeds. The Infeeds can, therefore, be
dimensioned so that each Infeed can provide half of the total current taking into account a small current derating
factor. If one Infeed fails, only half of the power required will be available. If the full power is required when one Infeed
fails, each Infeed must be dimensioned to provide the full power.
With variant 2, both redundant Infeeds with the same power rating are also supplied from one supply system, but via
a three-winding transformer. The transformer must be designed for redundant operation and be capable of
withstanding up to 100% asymmetrical loading. Depending on the characteristics of the transformer, the line-side
voltages of both Infeeds can have small tolerances of approx. 0.5 % to 1 %. This leads in normal operation with
unregulated Infeeds to a current distribution which is slightly less symmetrical than with variant 1. This must be must
be taken into account and covered by corresponding current derating factors. If the full power is required when one
Infeed fails, each Infeed must be dimensioned to provide the full power.
With variant 3, both redundant Infeeds with the same power rating are supplied by two independent supply systems
with two separate two-winding transformers. As the voltages of both independent supply systems can be noticeably
different, very large imbalances in the current distribution can occur in normal operation with unregulated Infeeds. If
voltage tolerances between the two supply systems of between 5 % and 10 % have to be dealed with, it is absolutely
necessary, when using unregulated Infeeds, to dimension each Infeed to provide the full power to connected DC
configuration.
Note:
The infeeds labeled "Infeed 1" and "Infeed 2" in the sketch can comprise in each case a single power unit (Power
Module), or a parallel connection of two identical power units (Power Modules). It is basically also possible to
configure parallel connections comprising more than two power units (Power Modules) per "Infeed". In this case,
detailed clarification of the relevant boundary conditions must be requested.
The following paragraphs will explain which of the three redundant line supply concepts (variants 1 to 3) can be
realized with the three Infeed types available with SINAMICS (Basic Infeed, Smart Infeed, Active Infeed) and which
boundary conditions must be observed.
Redundant line supply concepts with the SINAMICS Basic Infeed
With the line-commutated, unregulated SINAMICS Basic Infeed all three variants can be used.
Variant 1 with SINAMICS Basic Infeed, boundary conditions to be observed:
·
For each Basic Line Module a line reactor with a short-circuit voltage of 2 % is required.
·
If it can be accepted that the common DC link is operating with half the power when a Basic Line Module
fails, each Basic Line Module can be selected for half the input current taking into account a current derating
of 7.5 % related to the rated current, as with the 6-pulse, parallel connection of Basic Line Modules. If the full
power is still required by the common DC link when a Basic Line Module fails, each Basic Line Module must
be selected for the full power.
·
Each Basic Line Module must be able to precharge the complete common DC link capacitance.
Variant 2 with SINAMICS Basic Infeed, boundary conditions to be observed:
·
If the three-winding transformer corresponds to the specification in the section "Transformers", subsection
"Three-winding transformers", line reactors are not required.
·
If the three-winding transformer corresponds to the specification in the section "Transformers", subsection
"Three-winding transformers", and it can be accepted that the common DC link is operating with half the
power when a Basic Line Module fails, each Basic Line Module can be selected for half the input current
taking into account a current derating of 7.5 % related to the rated current, as with the 12-pulse, parallel
connection of Basic Line Modules. If the full infeed power is required when a Basic Line Module fails, each
of the two Basic Line Modules and their associated transformer windings must be dimensioned in line with
the full power required for the DC link.
·
Each Basic Line Module must be able to precharge the complete common DC link capacitance.
Variant 3 with SINAMICS Basic Infeed, boundary conditions to be observed:
·
A line reactor with a short-circuit voltage of 2 % is not required.
·
Due to the possibility of large voltage tolerances between both supply systems, it is absolutely necessary
that each Basic Line Module is configured for the full power required by the common DC link.
·
Each Basic Line Module must be able to precharging the complete common DC link capacitance.
Fundamental Principles and System Description
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