Siemens SINAMICS G130 Engineering Manual page 107

Fundamental Principles and System Description
Engineering Information
Precharging with S150 converters and S120 Active Infeeds via precharging contactor and precharging resistors
Due to the power losses which occur during precharging in the resistors, complete precharging of the DC link is only
permitted every 3 minutes and the permissible DC link capacitance of the connected inverter(s) is limited to a
relatively low value.
The maximum permissible DC link capacitance for the different S120 Active Interface Modules / Active Line Modules
can be found in the section "Checking the maximum DC link capacitance" of the chapter "General Information about
Built-in and Cabinet Units SINAMICS S120".
In the case of S120 Active Line Modules in Chassis format with Active Interface Modules in frame sizes FI and GI,
the precharging circuit (precharging contactor and precharging resistors) and the bypass contactor are integral
components of the Active Interface Module. The precharging circuit in the Active Interface Module is designed short-
circuit proof. The customer is not required to provide fuse protection for the precharging circuit in this case.
In the case of S120 Active Line Modules in Chassis format with Active Interface Modules in frame sizes HI and JI, the
bypass contactor is not an integral component of the Active Interface Module. The bypass contactor, which can be a
contactor or a circuit breaker depending on power rating, must be provided by the customer and also the fuse
protection for the precharging circuit must be provided by the customer. The fuses 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".
In the case of S120 Active Line Modules with Active Interface Modules in Cabinet Modules format, it is either not
necessary to provide fuse protection for the precharging circuit (short-circuit proof design in the Active Interface
Modules in frame sizes FI and GI), or the precharging circuit is protected by fuses inside the Line Connection Module
that is connected upstream of the Active Line Module with Active Interface Module.
IMPORTANT:
It is absolutely essential that the precharging contactor and the bypass contactor are controlled by the internal
sequence control of the S120 Active Line Module (precharging contactor via connector -X9:5,6 and bypass contactor
via connector -X9:3,4). When a circuit breaker is used as bypass contactor, it is essential that breaker opening is
controlled 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 make a parallel connection of up to four S120 Active
Line Modules with the matching Active Interface Modules. Further details can be found in the section "Parallel
connections of converters".
Due to the principle of active pulsing combined with the line-side Clean Power Filter, the harmonic effects on the
supply caused by the Active Infeed are virtually non-existent. The harmonic content of the line current is only very
minor, meaning that there are scarcely any harmonics in the line voltage either. The vast majority of current and
voltage harmonics is typically significantly lower than 1 % of rated current or rated voltage with the Active Infeed. The
total harmonic distortion factors of the current THD(I) and the voltage THD(V) are typically within a range of
approximately 3 %. When self-commutated IGBT Infeeds (S150, S120 Active Line Modules) are used, the system
complies with the limit values stipulated in standard IEEE 519 (Recommended Practices and Requirements for
Harmonic Control in Electrical Power Systems).
The criteria for defining of the required transformer power rating, taking into account the harmonic load are described
in the section "Transfomers".
Operation of the Active Infeed with a line-side power factor of cosφ < 1
When the Active Infeed, for which the line-side reactive current can be freely parameterized in the firmware, is
operated with a power factor of cosφ < 1, the power losses in the Active Line Module increase. For this reason, the
line current must be reduced in accordance with the derating characteristic shown below.
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Ó Siemens AG