
AC Power Fundamentals 21
unit of volt-ampere reactive (VAR, or kVAR, or MVAR). The power factor cosθ of
the load has no units. The complex power S
˜
, being the product of volts and amperes,
has the unit of volt-ampere (VA, or kVA, or MVA).
∴Complex power S∠θ = P + j Q is a phasor, with Q out of phase by + 90° from
P as shown by the Power Triangle in Figure1.12. The trigonometry of power tri-
angles gives
S P Q= +
2 2
or
kVA kW kVAR= +
2 2
and
pf
P
kW
= =
or kW = KVA × pf (1.27)
It is noteworthy that the lagging power factor of the load circuit produces a positive
Q, and vice versa. Also, in complex power S
˜
= S∠θ = V
rms
⋅