Cohabitation of high and low currents

Abstract

In our society today, the rapid development of digital systems using low current links (bus) has given rise to the critical problem formed by cohabitation of high and low currents.

The real problem is how to reconcile electrical safety and electromagnetic compatibility.

The following issues thus arise for which solutions must be found:

• how to treat the problem of exposed conductive parts,
• which earthing system should be chosen,
• which shields, mitigating planes, Faraday cages should be chosen and for what purpose,
• how to organise routing of high and low current circuits,
• and many others.

Although written with electrical engineers in mind, this Cahier Technique will certainly also be of interest to low current specialists since it mainly deals with low frequency disturbances of ≤1 MHz.

EMC: a discipline covering many professions

Electromagnetic compatibility (EMC), a rapidly developing field, came into being with the start of radio broadcasting. One of the first applications, a half-century ago, was the shields of sparkplugs of internal combustion engines to avoid
interference with radios receivers. Today, EMC is the subject of numerous studies carried out by experts, particularly in the fields of electronics and telecommunications.

Many standards and even an european directive have been published to ensure the cohabitation of disturbing and disturbed devices and systems. For this, they set electromagnetic disturbance emission limits and immunity levels.

AUTHOR: Schneider Electric experts | Roland CALVAS, Jacques DELABALLE