AC (alternating current) fundamentals involve understanding the behavior of electrical quantities that vary with time, such as voltage and current, in circuits that utilize sinusoidal waveforms. When working with AC circuits, it's common to use phasors, which are complex numbers that represent the amplitude and phase angle of the sinusoidal quantities.
Powers of Phasors:
The power associated with AC circuits is calculated using complex power, which takes into account both the real (active) power and the reactive power. Complex power is represented by the phasor "S" and is given by the product of voltage phasor "V" and current phasor "I*" (conjugate of current phasor):
=
∗
S=VI
∗
Real Power (P): This is the actual power dissipated in the circuit, which performs useful work. It's the real part of the complex power:
=
Re
(
)
P=Re(S)
Reactive Power (Q): This is the power that flows back and forth between the source and reactive elements (like inductors and capacitors) without performing any net work. It's the imaginary part of the complex power:
=
Im
(
)
Q=Im(S)
Apparent Power (|S|): This is the magnitude of the complex power and represents the total power delivered to the circuit, considering both real and reactive power components: