Anti-Resonant Harmonic Filters

An anti-resonant harmonic filter is a reactor wired in series with a power-factor-correction capacitor bank so the reactor-capacitor combination is tuned below the lowest significant harmonic present on the system, instead of resonating with it and amplifying that harmonic. Single-phase units cover ratings to 15 kVAR and three-phase units span 0.5 to 60 kVAR, wound with aluminium or copper conductor and terminated by terminal, lug, or busbar connection depending on current. The detuning factor, p%, expresses the reactor's reactance at the fundamental frequency as a percentage of the capacitor's reactance; the resulting tuning frequency moves further below the fundamental as p% increases, and it must be chosen from the harmonic spectrum actually present at the installation rather than assumed. A reinforced three-phase sub-series is built for sites with heavier harmonic loading or duty cycle than the standard three-phase line calls for.