14

04/00

2.2

Interference sources and disturbed equipment

Interference source

An interference source is an electrical device or electrical equipment which emits electromagnetic

interference. We can differentiate between two main groups of interference sources corresponding

to the type of frequency spectrum emitted (fig. 5).

Fig. 5

Sources of interference

Interference sources with discrete frequency spectra (e.g. high frequency generators and micro-

processor systems) emit interference energy which is concentrated on narrow frequency bands.

Switchgear and electric motors in household appliances, however, distribute their interference en-

ergy over broad frequency bands and are considered to belong to the group of interference sources

having a continuous frequency spectrum.

µP systems

Switchgear (contactors, relays)

RF generators

Household appliances

Medical equipment

Gas discharge lamps

Data processing systems

Power supplies and battery chargers

Microwave equipment

Ignition systems

Ultrasonic equipment

Welding apparatus

RF welding apparatus

Motors with brushes

Radio and TV receivers

Oscillating drives

Switch-mode power supplies

Atmospheric discharges

Frequency converters

UPS systems

Electronic ballast circuits

Interference source (emission)

Discrete frequency spectrum

(Sine-wave, low energy)

Continuous frequency spectrum

(Impulses, high energy)

General Technical Information