Sinamics Infeeds And Their Properties; Basic Infeed - Siemens SINAMICS G130 Engineering Manual

Fundamental Principles and System Description
Engineering Information
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SINAMICS Infeeds and their properties

Basic Infeed

The Basic Infeed is a robust, unregulated infeed for two-quadrant operation (i.e. the energy always flows from the
supply system to the DC link). This Infeed is not designed to regenerate energy from the DC link back to the supply
system. If regenerative energy is produced for brief periods by the drive, e.g. during braking, it must be converted to
heat by a Braking Module connected to the DC link combined with a braking resistor.
The Basic Infeed consists of a line-commutated, 6-pulse, three-phase rectifier equipped with thyristors or diodes. A
line reactor with a relative short-circuit voltage of 2 % is generally connected on the line side. Further details can be
found in the section "Line reactors" and in the chapters on specific unit types.
The Basic Infeed is an integral component of SINAMICS G130 chassis units and SINAMICS G150 cabinet units (with
thyristors in each case). It is also available as a stand-alone infeed in the SINAMICS S120 modular system, in
Chassis and Cabinet Modules format (with thyristors for the lower power ratings and with diodes for the higher power
ratings 900 kW/400 V and 1,500 kW/500 V-690 V).
SINAMICS S120 Basic Infeed comprising a Basic Line Module with thyristors and a line reactor with u
The Basic Infeed is a line-commutated rectifier which, from the three-phase line voltage V
unregulated, load-dependent DC link voltage V
line voltage value, i.e. V
DCLink
DC link voltage will be V
DCLink
As the DC link voltage is unregulated, line voltage fluctuations cause the DC link voltage to fluctuate correspondingly.
The processes for precharging the connected DC link are very different depending on the device variant used:
In the case of SINAMICS G130 and G150 converters in which the Basic Infeed is an integral component of their
power units, a small precharging rectifier equipped with diodes is connected in parallel with the main rectifier
equipped with thyristors. If this arrangement is applied to the voltage at the line side, the DC link is charged by means
of the precharging rectifier and the associated precharging resistors.
The principle of precharging involves the use of ohmic resistors and is, therefore, subject to losses. This means that
the precharging resistors must be thermally dimensioned to support precharging of the DC link for their G130 or
G150 converter without becoming overloaded. Additional DC link capacitances cannot be precharged. For this
reason, other S120 Motor Modules, for example, must not be connected to the DC link of a SINAMICS G130 or G150
converter.
In the case of Basic Line Modules for the SINAMICS S120 modular system equipped with thyristors, the DC link is
charged via the rectifier thyristors by changing the firing angle (phase angle control). During this process, the firing
angle is increased continuously for 1 second until it reaches the full firing angle setting. This precharging principle
results in hardly any losses, which means that an extremely high DC link capacitance could be precharged. The
permissible DC link capacitance for the connected inverters (S120 Motor Modules), however, must be limited to
protect the thyristors against an excessive recharge current entering the DC link capacitance when the voltage is
restored following a line voltage dip. Despite this, the limit for the permissible DC link capacitance is relatively high
due to the robust line-frequency thyristors.
The maximum permissible DC link capacitance for the different S120 Basic Line Modules can be found in the section
"Checking the maximum DC link capacitance" of the chapter "SINAMICS S120, General Information about Built-in
and Cabinet Units".
SINAMICS Engineering Manual – May 2008
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© Siemens AG
. Under no-load conditions, the DC link is charged to the peak
DCLink
= 1.41 • V When loaded the DC link voltage decreases. When partially loaded the
Line.
≈ 1.35 • V
and at full load,
Line
V = 1.32 • V
DCLink Line.
= 2%
k
produces an
Line,