The Frequency Converter As A High-Frequency Source Of Interference - Siemens SINAMICS G130 Engineering Manual

EMC Installation Guideline
Engineering Information
2.3.2

The frequency converter as a high-frequency source of interference

The main source of high-frequency interference is the fast switching of the IGBTs (Insulated Gate Bipolar
Transistors) in the motor-side inverter, which results in extremely steep voltage edges. Each voltage edge generates
a pulse-shaped leakage or interference current I
Schematic representation of inverter output voltage V and interference current I
The interference current I
I
C , and must return to its source (the inverter) via a suitable route. The interference current I
P
inverter via the ground impedance Z
consists of the parallel connection of the transformer impedance (phase to ground) and parasitic capacitances of the
supply cable (phase to ground). The interference current itself as well as the interference voltage drops caused by
the impedances Z and Z
Ground
Schematic representation of the generation of the interference current I
Measures for reducing high-frequency conducted interference emissions
When unshielded motor cables are used, the interference current I
grounding system, and supply impedance and can generate high interference voltages via impedances Z
Z due to its high frequency.
Line
The effect of interference on the grounding and supply system by the interference current I
reduced by leading the high-frequency interference current I
such a way that the voltage drops via impedances Z
filter or EMC filter (RFI suppression filter) integrated as standard in SINAMICS devices (according to category
C3 of EMC product standard EN 61800-3), the high-frequency interference current I
route back to the inverter within the drive system. This means that most of the interference current I
shield of the motor cable, the PE or EMC shield busbar, and the line filter. The standard line filters are provided in
SINAMICS G130, G150, and S150 converters as well as in the infeeds of the SINAMICS S120 modular system
(Basic Line Modules, Smart Line Modules, and Active Line Modules including the associated Active Interface
Modules, in Chassis and Cabinet Modules format). As a result, the grounding and supply system are subject to much
lower interference currents and the interference emissions are considerably reduced.
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via the parasitic capacitances at the inverter output.
I
flows from the motor cable and the motor winding to ground via the parasitic capacitances
and the supply impedance Z
Ground
can affect other devices connected to the same supply and grounding system.
Line
I
, whereby the supply impedance Z
Line
and its route back to the inverter
I
flows back to the inverter via cable rack,
I
back to the inverter using a shielded motor cable in
I
and Z are minimized. In combination with the line
Ground Line
flows back to the
I
Ground
can be considerably
I
can flow via a low-resistance
I
flows via the
I
Line
and