 Leading power factor

A leading power factor describes an absorbing sinusoidal electrical load whose electric current leads its terminal electric potential difference. Under the passive sign convention, writeThe current maximum occurs earlier by $\theta /\omega$. The complex electrical power isThe negative reactive power is consistent with a capacitive terminal response. It does not imply negative mean absorbed active power.

For an original $100\mathrm{V}$, $2\mathrm{A}$ example with $\theta =\pi /3$, the power factor magnitude is $0.5$, active power is $100\mathrm{W}$, and reactive power is $-100\sqrt{3}\approx -173.21\mathrm{var}$. At $50\mathrm{Hz}$ the current leads by $1/(6f)\approx 3.33\mathrm{ms}$. A load with the same RMS magnitudes and the opposite phase displacement has identical active power but a lagging power factor and opposite reactive power.

For an ideal capacitor, $i=Cdv/dt$ gives a quarter-cycle current lead. Its mean active power is zero, although instantaneous power alternates as electrical energy enters and leaves the field. The primary one-frequency power derivation separates this quadrature exchange from net energy transfer.^[ref]

An inductive load can acquire a leading power factor at the source when power factor correction supplies more capacitive reactive power than the load absorbs. The current reduction interval for shunt reactive compensation shows why mildly leading operation can still draw less source electric current than no correction, while excessive correction reverses that benefit.

Record phase direction or signed reactive power together with the numerical factor. The same positive cosine can describe leading and lagging loads, and a meter may assign a separate sign according to its display convention.^[ref] For nonsinusoidal signals, state whether leading describes the fundamental displacement power factor; the complete power factor also depends on waveform distortion.