Harmonics (THD)
Harmonischen (THD)
Multiples of the mains frequency (150 Hz = 3rd, 250 Hz = 5th, ...) fed back by non-linear loads (inverters, LED drivers, IT power supplies), expressed as THD. Triplen harmonics (3rd, 9th) add up in the neutral and can load it beyond the phases — a cause of overheated N conductors and transformer hum.
Practical example
Harmonics (THD): On an office floor with many IT power supplies, current in the neutral conductor exceeds phase currents due to summation of the 3rd harmonic component.
Common mistake
Harmonics (THD): Size neutral as phase for heavy IT loads — triplen harmonics can make N current exceed phase current; provide a full or reinforced neutral.
See also
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