Smart Infeed - Siemens SINAMICS G130 Engineering Manual

Fundamental Principles and System Description
Engineering Information
The precharging circuit consists of a precharging contactor and precharging resistors and their fuse protection.
For S120 Basic Line Modules in Chassis format (equipped with diodes), the precharging circuit including its fuse
protection must be provided by the customer. The components recommended for this purpose can be found in
section "Precharging of the DC link and precharging currents" of chapter "General Information about Built-in and
Cabinet Units SINAMICS S120".
For S120 Basic Line Modules in Cabinet Modules format (equipped with diodes), the precharging circuit including its
fuse protection is always located in the Line Connection Module LCM that is connected upstream of the Basic Line
Module (equipped with diodes).
The bypass contactor is a circuit breaker.
For S120 Basic Line Modules in Chassis format (equipped with diodes), the bypass contactor (circuit breaker) must
be provided by the customer.
For S120 Basic Line Modules in Cabinet Modules format (equipped with diodes), the bypass contactor (circuit
breaker) is always located inside the Line Connection Module LCM that is connected upstream of the Basic Line
Module (equipped with diodes).
IMPORTANT:
It is absolutely essential that the precharging contactor and the bypass contactor are controlled by the internal
sequence control of the S120 Basic Line Module (equipped with diodes) (precharging contactor via connector -X9:5,6
and bypass contactor (circuit breaker) via connector -X9:3,4). It is essential that the circuit breaker is opened by an
instantaneous release. For this reason, only circuit breakers equipped with instantaneous undervoltage release may
be used.
To achieve an increased output power rating, it is possible to connect up to four S120 Basic Line Modules in parallel
(including 6-pulse and 12-pulse configurations). Further details can be found in the section "Parallel connections of
converters".
Due to the operating principle of the 6-pulse three-phase bridge circuit, the Basic Infeed causes relatively high
harmonic effects on the supply system. The line current contains a high harmonic content with harmonic numbers
h = n 6 ± 1, where n assumes integers 1, 2, 3, etc. The Total Harmonic Distortion factor of current THD(I) is
*
typically in the range from about 30 % to 45 %. For further information about harmonic characteristics, please refer to
the section "Harmonic effects on the supply system". Line Harmonics Filters LHF can be installed on the line side of
G130 Chassis units and G150 cabinet units in order to reduce the effects of harmonics on the supply. These reduce
the total harmonic distortion factor THD(I) to below 7.5 %. A similar reduction can also be achieved with 12-pulse
circuits, i.e. by supplying two Basic Line Modules from a three-winding transformer with a 30 ° phase displacement
between its voltages.
The criteria for defining of the required transformer power rating, taking into account the harmonic load as well as the
characteristics of three-winding transformers in 12-pulse operation, are described in the section "Transfomers".
1.6.2

Smart Infeed

The Smart Infeed is a stable, unregulated rectifier / regenerative unit for four-quadrant operation, i.e. the energy flows
from the supply system to the DC link and vice versa. The current values stated in the catalogs are available in both,
rectifier and regenerative operation.
The Smart Infeed consists of an IGBT inverter, which operates on the line supply as a line-commutated 6-pulse
bridge rectifier / regenerative unit. In contrast to the Active Infeed, the IGBTs are not active pulsed using the pulse-
width modulation method. In rectifier operation (motor operation) the current flows via the diodes integrated into the
IGBT modules from the line supply to the DC link, so that a line-commutated, 6-pulse diode bridge circuit is present in
motor operation. In regenerative operation the current flows via the IGBTs, which are synchronised at the line
frequency. Thus, a line-commutated, 6-pulse IGBT bridge circuit is present at regenerative operation.
As IGBTs, in contrast to thyristors, can be switched off at any time, inverter shoot-through during regenerative
operation caused by supply system failures cannot occur in contrast to rectifier / regenerative units equipped with
thyristors.
On the line side, the Smart Infeed is normally equipped with a line reactor having a relative short circuit voltage of
v = 4 %.
k
The Smart Infeed is available as a stand-alone Infeed of the SINAMICS S120 modular system in Chassis and
Cabinet Modules format.
SINAMICS Engineering Manual – November 2015
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Ó Siemens AG