Siemens SINAMICS G130 Engineering Manual page 66

Fundamental Principles and System Description
Engineering Information
Due to the power losses which occur during precharging in the resistors, 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 "SINAMICS S120, General Information about Built-in and Cabinet Units".
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. Each individual current harmonic and
voltage harmonic is typically below 1% of the rated current or rated voltage with an Active Infeed. The Total Harmonic
Distortion factors of the current THD(I) and voltage THD(U) are typically less than 3%
The criteria for defining of the required transformer power rating, taking into account the harmonic load are described
in the section "Transfomers".
Creating a separate network with the Active Infeed
The SINAMICS Active Infeed is designed as an Infeed component for SINAMICS drive systems. Therefore, it must
be connected to an existing, three-phase supply system. By means of the Voltage Sensing Module VSM integrated
into the Active Interface Module AIM, it measures the voltage of the supply system according to magnitude and
phase angle, synchronises itself on the supply voltage and frequency and regulates the DC link voltage for the
connected drive configuration to a constant value, which can be parameterized.
A separate network cannot currently be created by means of an Active Infeed since it is not equipped with a line
frequency generator and line frequency controller. For this reason, applications that need to create a separate
network by means of a self-commutated, line-side converter as an interface to the supply system are currently not
compatible with SINAMICS Active Infeeds. Such applications include:
•
Wind power plants with Active Infeeds for creating local separate networks
•
Solar power systems with Active Infeeds for creating local separate networks
•
Diesel-electric emergency power supply sets with Active Infeeds for creating local separate networks
•
Wave generators on ships with Active Infeeds for creating on-board supply systems
Note:
The fact that the Active Infeed does not have a line frequency generator can lead to critical operating conditions if an
Active Infeed in no-load operation is separated from the supply system by the opening of the main contactor or the
circuit breaker without a preceeding OFF command. Therefore, it is absolutely essential that the operation of the
Active Infeed is always stopped with an OFF command before it is separated from the supply system.
SINAMICS Engineering Manual – May 2008
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