Earthing Of Shielded Cables; Shielded Cables Increase Interference Resistance - Emerson PACSystems RSTi-EP User Manual

User Manual
GFK-2958J
Figure 214: Connection Diagram of a Frequency Converter
7.1

Earthing of Shielded Cables

Electrical and electronic systems must be designed such that they are largely safeguarded
against electrical interference, thus enabling them to operate securely even in the case of
transient interference voltages.
Electrical interference can be introduced into electric circuits in a variety of ways. The most
frequent causes are due to inductive interference. In addition, galvanic and capacitive
coupling as well as electrical fields and other processes are causes for interference
voltages. Here, high-frequency voltage fluctuations – known as transients – are the cause
of interference with a high level of effectiveness.

Shielded Cables Increase Interference Resistance

The sources of interference voltages can rarely be eliminated, and even then, not always
completely. Thus, it is necessary to take measures to combat their effect. In general, the
more effectively interference voltages can be kept away from circuit elements or can be
discharged, the less electrical circuits are affected. This can be accomplished in a variety of
ways with varying levels of effectiveness. A very effective measure, for safeguarding against
inductive effects, that is, ensuring electromagnetic compatibility (EMC), is the shielding of
electrically functional components to earth potential. In doing so, for instance, components
are installed in metallic, earthed housings and the connecting lines are equipped with
shielding.
Earthing and shielding
Chapter 7
Oct 2019
339