Power Factor

Power factor is defined as the ratio of real power to apparent power. It shows how efficiently the capacity of a system of a system (represented by apparent power) has been utilized.

$$\text{PF}=\frac{P}{|S|}=\cos ({\theta }_v-{\theta }_i)$$

We must specify whether a power value is lagging or leading:

• Lagging power factor: $\vec{I}$ lags $\vec{V}$
  • Inductive load, $Q>0$, such that $Q$ is drawn by the load
• Leading power factor: $\vec{I}$ leads $\vec{V}$
  • Capacitative load, $Q<0$ such that $Q$ is delivered by the load

$Q$ is reactive power!

Ideally, the largest possible portion of the capacity of the system is dedicated to handling real power; as such, it is desirable to achieve as high a power factor as possible, ideally a unity power factor.