Power factor
The power factor or cos φ as applied to electrical engineering describes the relationship between effective power Pe and apparent power Pa with respect to AC circuits.
Apparent power is the product of a phase shift between voltage and current. Inductive and capacitive resistors in AC circuits effect a shift in the current curve with respect to voltage. This shift is described by angle φ.
The phase shift between voltage and current is + 90 degrees for capacitance and - 90 degrees for inductance. Phase shifts do not occur with ohmic resistance. Mixed resistance refers to impedance, whose phase displacement angles lie between 0 degrees and + 90 degrees and 0 degrees and – 90 degrees.
The power factor for pure sinusoidal current and voltage is equivalent to the cosine of the phase displacement angle (φ). It is used to calculate the effective current (Ie) and effective power (Pe):
Power companies frequently require a minimum power factor of 0.9 from customers. When this value is undershot, the reactive energy consumed is invoiced separately. Reactive power compensation systems can be used to increase the power factor:
