Electromagnetic Compatibility (EMC)

The term EMC (Electromagnetic Compatibility) encompasses a wide range of phenomena. These are primarily distinguished by how they propagate (conducted via cables or radiated through space) and how long they last (continuous or transient/short-duration).

The following is a systematic overview of the most important EMC phenomena:

1. Transient (short-duration, impulsive) phenomena

These disturbances occur suddenly and often last only microseconds to milliseconds, but can involve extremely high energy levels or voltage peaks.

ESD (Electrostatic Discharge): A spark discharge caused by static electricity (e.g. a person touching an enclosure).

Burst (Electrical Fast Transients): Sparking when switching inductive loads (e.g. contactors, relays or motors).

Surge (Surge Voltages): High-energy impulses, usually triggered by lightning strikes or major switching operations in the power supply network.

Voltage Dips & Interruptions: Sudden fluctuations in the mains voltage caused by load changes in the power grid.

2. Continuous (persistent) phenomena

These disturbances are present continuously or over extended periods.

High-frequency electromagnetic fields: Radio waves from mobile communications (5G, LTE), Wi-Fi, Bluetooth, broadcasting transmitters or radar systems.

Harmonics: Power supply distortion caused by non-linear loads (e.g. LED drivers, power supplies and frequency converters) that distort the sinusoidal current waveform.

Mains Hum / Power-frequency Magnetic Fields: Radiated 50 Hz or 60 Hz fields from transformers, high-voltage power lines or underground cables.

Voltage Fluctuations and Flicker: Regular fluctuations in the mains voltage that cause visible flickering of light sources.

Classification by Propagation Path

For practical EMC testing and development, these phenomena are strictly divided into two categories:

Conducted Phenomena (via Cables)

  • Harmonics
  • Burst impulses on data/power lines
  • Surge (lightning-induced surge voltages)
  • Mains voltage flicker and dips

Radiated Phenomena (through the Air)

  • RF fields from radio systems (mobile communications, Wi-Fi)
  • Radiated interference fields from switched-mode power supplies
  • Magnetic fields from transformers
  • Indirect effects of nearby ESD discharges
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