• summary_type: application
• word_count: 160

Average power in AC: P = V_rmsI_rmscos(phi). The power factor cos(phi) = R/Z ranges from 0 (pure L or C) to 1 (pure R or resonance). The current can be decomposed into two components: active current Icos(phi) (in phase with V, delivers real power) and reactive/wattless current Isin(phi) (90 degrees out of phase, delivers zero net power). Wattless current flows through inductors and capacitors — it creates magnetic and electric fields but returns the energy each half cycle. Although it delivers no power, wattless current increases the total current drawn, causing extra I^2R losses in transmission lines. Power companies penalize industrial consumers with low power factor (< 0.85). To improve power factor, a capacitor is connected in parallel with inductive loads (motors, transformers) to cancel the reactive component. At resonance, cos(phi) = 1 and wattless current is zero.