Power Factor

The power factor $pf$ is a value between $0\le |pf|\le 1$. It represents the percentage of power that is real/active power.

$pf=\cos ({\theta }_v-{\theta }_i)$ $P=V_{rms}{I}_{rms}\cdot pf$

Lagging vs Leading

1. $pf$ lagging means $\tilde{I}$ lags $\tilde{V}$, or $Q$ positive (inductive)
2. $pf$ leading means $\tilde{I}$ leads $\tilde{V}$, or $Q$ negative (capacitive)

Rule of Thumb for Commercial Buildings

• Good $pf$: 1.0 - 0.95
• Poor $pf$: 0.95 - 0.85
• Bad $pf$: 0.85 and below

Commercial buildings usually around 0.98 - 0.92

How to adjust power factor?

• We add capacitive load to a lagging (inductive) circuit
• We add inductive load to a leading (capacitive) circuit