Redundant Line Supply Concepts - Siemens SINAMICS G130 Engineering Manual

Fundamental Principles and System Description
Engineering Information
1.6.5 – – –
1.6.6

Redundant line supply concepts

General
Certain applications require redundant Infeeds for multi-motor drives or common DC link configurations to increase
availability. This demand can basically be fulfilled by using several independent Infeed units working in parallel on the
common DC link. If one Infeed unit fails the common DC link can be supplied by the remaining Infeed unit, usually
without interruption. Depending on the power rating of the Infeed units the common DC link can continue to operate
at between half and full power. This is dependent on fulfillment of the following requirements:
·
Each Infeed must have its own Control Unit.
·
The Control Unit of each Infeed must control only the assigned Infeed but not any additional Motor Modules.
·
Due to the need for redundancy, the Motor Modules operating on the common DC link must be operated on
a separate Control Unit or multiple separate Control Units in complete independence of the Infeed Modules.
The difference between redundant Infeeds and the parallel connection of Infeeds for increasing the power rating, as
described in the section "Parallel connections of converters", is the arrangement of the Control Units. At redundant
Infeeds each Infeed is controlled by its own Control Unit. Therefore, each Infeed is completely autonomous. At the
parallel connection of Infeeds, a single Control Unit controls and synchronizes all power units in the parallel
configuration, which behaves as a single Infeed with a higher power rating.
Note:
When several independent Infeeds are used, this can considerably increase the availability of the DC busbar. In
practice, however, 100 % fault tolerance is impossible since certain fault scenarios can still cause an interruption in
operation (such as a short circuit on the DC busbar). Even if these fault scenarios are extremely unlikely to occur, the
risk of their occurring cannot be completely eliminated in practice.
Depending whether the demand for redundancy is related only to the Infeed units or also to the supplying
transformers or the supply systems, different circuit concepts are possible, which are shown and explained below.
Supply
Control
Unit 1
Infeed 2
Infeed 1
M
Variant 1:
Supply from a single supply system
with a double-winding transformer
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Control
Unit 2
Variant 2:
Supply from a single supply system
with a three-winding transformer
Variant 3:
Supply from two independent supply
systems with two transformers