Apparent Power (S): Single phase: $S = V \cdot I$. Three phase: $S = \sqrt{3} \cdot V_{LL} \cdot I_L$
Real Power (P): $P = S \cdot \cos(\theta) = S \cdot PF$
Reactive Power (Q): $Q = S \cdot \sin(\theta) = \sqrt{S^2 - P^2}$
PFC Capacitor: Required compensation $Q_c = P \cdot (\tan(\theta_{old}) - \tan(\theta_{new}))$.
$C = Q_c/(2\pi f V^2)$ for single phase; $C_\Delta = Q_c/(3 \cdot 2\pi f V_{LL}^2)$ per branch for three-phase delta.
Sinusoidal steady-state, lagging displacement power factor only; three-phase assumes a balanced load and line-to-line RMS voltage. S = VI (single phase) or √3 VLL IL; P = S·PF, Q = S√(1−PF²). Correction Qc = P[tan(acos(PF))−tan(acos(target))]. Capacitance is per delta branch for three phase, or the single capacitor for one phase. Harmonics, resonances, switching and capacitor ratings require separate analysis.