The Frequency Converter As Potentially Susceptible Equipment; Methods Of Influence; Conductive Coupling - Siemens SINAMICS G130 Engineering Manual

The frequency converter as potentially susceptible equipment

Methods of influence

The interference generated from sources of interference can reach potentially susceptible equipment by different
types of coupling paths. A distinction is made here between conductive, capacitive, inductive, and electromagnetic
interference coupling.
Source of
interference
e.g.:
- Power unit of
- Switched-mode
- Motor cable
Possible paths between sources of interference and potentially susceptible equipment

Conductive coupling

Conductive coupling is established when several electrical circuits use a common conductor (e.g. a common ground
lead or ground connection). Current I
common conductor; which influences the voltage at the terminals of electronic board 2. Conversely, current I
electronic board 2 generates a voltage drop ΔV
voltage at the terminals of electronic board 1.
Conductive coupling of two electrical circuits by means of the impedance Z of a common conductor
If, for example, the voltage source V is a power supply unit that supplies two electronic boards with a DC voltage of
24 V, and electronic board 1 is a switched-mode power supply with a periodic, pulsating current consumption, and
electronic board 2 is a sensitive interface module for analog signal transmission, then electronic board 1 in this
scenario would be the source of interference. This disturbs the supply voltage at the terminals of the interface
module, which acts as potentially susceptible equipment, via the conductive coupling (i.e. via the voltage drop ΔV at
the common impedance Z). This can affect the quality of the analog signal transmission.
Measures for reducing conductive coupling
•
Minimize the length of the common conductor
•
Use large cable cross-sections if the common impedance is largely ohmic in character
•
Use a separate feed and return line for each electrical circuit
Coupling path
conductive
capacitiv
the converter
power supply
in the converter
electromagnetic
of electronic board 1 generates a voltage drop ΔV
1
at impedance Z of the common conductor; which influences the
2
EMC Installation Guideline
Potentially
susceptible
equipment
e.g.:
- Signal interface
- Encoder interface
inductiv
- Control Unit
SINAMICS Engineering Manual - May 2008
Engineering Information
at impedance Z of the
1
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© Siemens AG
of
2