# AC power

In an AC circuit, the voltage and current are varying, so the power can't be calculated with P = V·I. The (active) power can be calculated by multiplying the right side of the formula by cos(φ). cos(φ) is called the power factor and φ is the phase. The right side has to be multiplied with when three phase power is used instead of one phase.

### Formulas

#### One phase

#### Three phase

PF is the power factor.

P _{act } is the symbol for active power and is measured in watt (W).

P _{reac } is the symbol for reactive power and is measured in volt-ampere reactive (VAR).

P _{app } is the symbol for apparent power and is measured in volt-ampere (VA).

V is the symbol for voltage and is measured in volt (V).

I is the symbol for current and is measured in ampere (A).

φ is the symbol for phase and is measured in degrees.