Harmonic Distortion Calculator
Calculate total harmonic distortion (THD) from the fundamental and dominant harmonic component.
Total Harmonic Distortion
9.05 %
Total Harmonic Distortion vs Fundamental Component (V1 or I1)
Formule
## Total Harmonic Distortion (THD) THD quantifies how much the waveform deviates from a pure sinusoid. ### Formula **THD = sqrt(V3^2 + V5^2 + V7^2 + ...) / V1 x 100%** where V1 is the fundamental component and V3, V5, V7 are harmonic magnitudes. IEEE 519 recommends voltage THD below 5% at the point of common coupling for general systems.
Exemple Résolu
A 230V supply with 15V 3rd harmonic, 12V 5th, and 8V 7th.
- 01RSS harmonics = sqrt(225 + 144 + 64) = sqrt(433) = 20.81
- 02THD = 20.81 / 230 x 100 = 9.05%
- 03This exceeds the 5% IEEE 519 limit; mitigation is needed.
Questions Fréquentes
What causes harmonics in power systems?
Non-linear loads: variable frequency drives, rectifiers, switch-mode power supplies, LED drivers, fluorescent ballasts, and arc furnaces all draw non-sinusoidal currents that inject harmonics into the system.
What problems do harmonics cause?
Overheating of transformers and cables, nuisance tripping of breakers, interference with sensitive electronics, increased losses, and resonance with capacitor banks.
How are harmonics mitigated?
Passive harmonic filters tuned to specific frequencies, active harmonic filters that inject cancelling currents, 12-pulse or 18-pulse rectifier configurations, and phase-shifting transformers are common mitigation methods.
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