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mlight tech training: what is electromagnetic compatibility – emc?




What is EMC?

Electromagnetic compatibility (EMC) is the ability of a device or system to operate satisfactorily in its electromagnetic environment without causing unacceptable interference to other devices in the surrounding environment.

Electromagnetic interference (EMI) is the generation of electromagnetic energy, whether deliberate or accidental, by some source and its release into the environment.  The damaging effects of electromagnetic interference pose unacceptable risks in many areas of technology, and it is necessary to control such interference and reduce the risks to acceptable levels.

Electromagnetic noise is produced in the source due to rapid current and voltage changes, and spread via the coupling mechanisms described below.

Conductive Coupling occurs when the coupling path between the source and the victim is formed by direct electrical contact with a conducting body, for example through transmission or power cables, low voltage wiring, PCB trace or metal enclosure.

Methods to reduce conductive coupling include:

  • Ferrite beads around cables that suppress (attenuate) high frequency noise.
  • Increasing the distance between cables (ie. Separation of mains and low voltage DC).

Radiative Coupling occurs through radio-frequency interference (RFI) where the source and victim are separated by a large distance, typically more than a wavelength.  Source and victim act as a radio antennas: the source emits or radiates an electromagnetic wave which propagates across the space and is picked up or received by the victim.

Methods to reduce or remove radiated coupling include using:

  • Metal or plastic (conductive) enclosures around electronics which act as an interference shield.
  • Shielded cables, where the signal wires are surrounded by an outer conductive layer that is grounded at one or both ends.

A lighting manufacturer has an obligation to keep technical documents for any lighting products it places onto the Australian market.  These documents include a compliance folder for each product that contains; a description of the device, brochures or specification sheets, copies of any test reports and a signed DOC stating that the product complies with the relevant standard/s.

 

Written by Nathan Pleming