Siemens SINAMICS G130 Engineering Manual page 28

Fundamental Principles and System Description
Engineering Information
Supply of the auxiliaries with 230 V AC and of the electronics with 24 V. Example with a SINAMICS G150 cabinet unit.
The type of the SINAMICS Infeed (rectifier) determines the relationship between the supply voltage and the DC link
voltage. Further information on this can be found in the section "SINAMICS Infeeds (rectifiers) and their properties".
The line-commutated, unregulated Infeeds SINAMICS Basic Infeed and SINAMICS Smart Infeed generate a DC link
voltage, which is at stationary operation in proportion to the supply voltage. If the supply voltage dips, the energy flow
from the supply to the DC link is interrupted until the DC link voltage has, as a result of the load current, fallen to a
voltage level which corresponds to the supply voltage which has dipped. If this voltage level is below the under-
voltage trip level of the DC link, the energy flow from the supply to the DC link is completely interrupted. In this case
the drive can only use the electrical energy stored in the DC link capacitors and can only continue to operate until the
DC link voltage has dropped to the value of the under-voltage trip level by means of the load current on the motor
side. This time span is in the range of a few milliseconds and depends on the load conditions of the drive. It
decreases as the load increases so that at full load, only small supply voltage dips of a few milliseconds can be
overcome without fault tripping.
The self-commutated, regulated Infeed, SINAMICS Active Infeed, operates as a step-up converter and can regulate
the DC link voltage, almost independently of the supply voltage, to a constant value. As a result, the energy flow from
the supply to the DC link can also be maintained during serious supply voltage dips. As long as the reduced power,
as a result of the lower supply voltage, can be compensated for by a higher input current, the drive is able to
overcome large and long supply voltage dips, without a fault trip.
The following pages will deal with the behaviour of the unregulated and regulated SINAMICS Infeeds in view of the
above-mentioned considerations.
Permissible supply voltage dips with the unregulated SINAMICS Infeeds, Basic Infeed and Smart Infeed
In order to explain the behaviour of SINAMICS drives with line-commutated, unregulated Infeeds, all theoretically
possible supply voltage dips with regard to magnitude and duration are devided into six different ranges, named A to
F. In the following diagram, these ranges are shown for unregulated SINAMICS Infeeds, whereby each range
corresponds to different boundary conditions and, therefore, to a different behaviour of the drive.
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